Are you looking to use this system, or just part it out for sale? Do they need to function as new, or do you just need to describe them as working?
The Audio Research components are classic and can be refurbished at the factory. The same goes for the Mac tuner, the turntable and the speakers. Shipping them back to the factory and the service can run into considerable money. Some people thought the Tandberg was the best cassette deck ever made. Unfortunately, high end cassette decks are about as complicated as consumer audio components can get and parts for Tandbergs can be hard to find. Plus there is a limited market of pricey cassette buyers.
Regardless of your intention, it comes down to price. Are you talking hundreds of dollars or considerably higher amounts?